Project Setup: Node, TS with Jest

A simple project setup walkthrough to get you up and running with Jest on a Node project using Typescript.

Install dependencies

// Create directory
mkdir <project-name>
// Install node
npm init -y
// Install dependencies
npm i -D nodemon rimraf typescript ts-node ts-jest jest @types/jest @types/node
1) nodemon - restart the project when files change
2) rimraf - help deep delete files
3) typescript - typescript compiler
4) ts-node - run TS without compile and 'then' a run
5) ts-jest - TS and Jest
6) jest - test framework
7) @types/jest - Typescript Types for Jest
8) @types/node - Typescript Types for Node

Setup package.json

// package.json
{  
  "name": "node-typescript-jest-starter",
  "version": "0.0.1",  
  "description": "",
  "main": "dist/index.js",
  "scripts": {
    "build": "rimraf dist && tsc",
    "start": "node dist/index.js",
    "dev": "nodemon --exec ts-node src/index.ts --watch src",
    "test": "jest --watch",    
    "coverage": "jest --coverage"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@types/jest": "^23.3.11",
    "@types/node": "^10.12.18",
    "jest": "^23.6.0",
    "nodemon": "^1.18.9",
    "rimraf": "^2.6.3",
    "ts-jest": "^23.10.5",
    "ts-node": "^7.0.1",
    "typescript": "^3.2.2"
  }
}

Add git

git init

But don’t add everything to git

// .gitignore
node_modules
dist
coverage

Add Typescript Configuration

• Include only ts files in src folder, i.e. not dist (your compiled javascript)

// create config file
tsc --init
// .tsconfig
{
  "include": [
    "src/**/*.ts"
  ],
  "exclude": [
    "src/**/*/test.ts"
  ],
  "compilerOptions": {
    "target": "ESNEXT",
    "module": "commonjs",
    "outDir": "./dist",
    "rootDir": "./src",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true
  }
}

Add Jest Configuration

// create config file
jest --init
// jest.congig.js
module.exports = {
  preset: 'ts-jest',
  testEnvironment: 'node'
};

Create src and dist directories

touch dist src

Create a test

// src/blackjack.test.ts
import { score } from "./blackjack";
describe("blackjack", () => {
  describe("determine the score of a hand", () => {
    it('calculates a score correctly', () => {
      let hand = 2;
      expect(score(hand)).toEqual(2);
    })
  });
});

Run the test — which will run your test, and watch for changes.

npm run test

Write some Typescript — to pass the test

export const score = (hand: number) => {
  return hand;
};

… write some better tests and better code!